Just as Dean said, but i think you will have to drill some new holes in your GSR guards to be able to bolt it up on the corners as the evo bar is shorter than the GSR one on the sides and the evo bar bolt holes wont line up with the existing GSR guard. If its a fibreglass copy then it should bolt right on with no mods.
Ill be doing both GENUINE bumper and guards when im back from down south for work.
I believe you may also have to adapt some tabs to hold on/mate the bumper to the radiator panel.
Ill get some pics and write up after I do it